Method of preserving wood



UNITED STATES MAX RUPING, OF BERLIN, GERMANY.

METHOD OF PRESERVING WOOD.

No Drawing.

To all whom it may concern:

lie it known that I, Max Riimxo, a subject of the (ierman Emperor 3residing at mssingstrasse l, in the city of lie'rli'n. N. h, 23,(iermany, have invented certain new and useful Improvements in Methodsof Preserving \Vood; and I do hereby declare the following to be a full.clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

My present invention relates to an improvement in the method ofpreserving wood by coating or painting the walls of the cells of thewood with a preservative liquid,

after the manner described in my Reissue latent X0. 12707, grantedOctober 22, 1907, entitled Method of impregnating wood.

According to the invention described in that patent, the wood was firstsubjected for some time to air under pressure, which air permeated thepores and cells of the wood..

While the wood still contained the air under pressure. as beforedescribed, it was submerged in a bath of preservative material, at astill higher pressure, causing the liquid to enter the pores and cellsof the wood. Due to capillary attraction, this liquid would follow thewalls of the cells or pores, leaving the air in the form of globulesimprisoned in the liquid, but not in contact with the walls of the cellsor pores; then when the pressure was suddenly removed, the imprisonedair blew out the excess of liquid in the pores or cells, leaving thewalls of the cells painted with the preservative compound.

According to my present invention I pur-' pose to modify the first stepof the process thus described. by preheating the air which is suppliedto the pores of the wood, thereby securing certain advantages that willbe hereinafter. described.

The heated air may be either at or near atmospheric pressure, but bettercontrol of the amount of preservative liquid. injected into the wood,and quicker treatment are secured by using the heated air. at a pressureconslderably above atmospheric pressure, for instance from to 100 poundspressure per square inch.

The air may be heated either in the chamber itself, or may be sup liedto the chamber in the heated condition, and the wood should be subjectedto this heated air for a period depending in a large measureuponSpecification of Letters Patent.

' in advance.

Patented June 29, 1920.

Application filed December 14, 1918. Serial No. 136,947,

high enough to char the wood; or, when a preservative such as creosoteoil is used, which gives off explosive gases when heated, thetemperature should not be high enough to explode the gases generatedfrom the presence of more or less of the preservative material eitherremaining in the heating chamber or admitted thereto.

'here the wood is dry and porous, the time for which it is required tobe exposed to the heated air would be materially less than where thewood is dense or not well dried; and in "a similar way the temperatureof the heated air need not be so high where the wood has been thoroughlydried I cannot, therefore, state any fixed time during which the woodshould be exposed to the action of the heated air, or the temperature ofthe air, except that this temperature should preferably range between 50and 110 C, and the time between two and six hours. Of course, with alower temperature the wood would ordinarily need to be subjected to theaction of the heat longer than where the temperature was higher.

.As a specially suitable liquid preservative for use inthis process,creosote oil might be mentioned, and the process will now be describedwith special reference to the use of this preservative.

After the wood has become thoroughly impregnated with the heated air,preferably under pressure; the creosote oil is forced in, preferabl alsoheated to a tem erature of not less t an 70 0., nor more t an 95 C., andat a higher ressure than the air already in the retort. The heating ofthe creosote oil will make it more fluid, and it will flow more readilyinto the pores and cells of the wood, and at the same time it willimprison the air globules therein; the capillary attraction of the sidewalls of the pores or cells serving to draw the fluid creosote oil intothe innermost recesses of the wood and effectu'all coating the walls ofthe pores or cells as a ove referred to.

The drying action of the preliminary heated air will serve not onlytoevaporate much of the moisture still remaining in the wood, but willmore especially leave the walls of the pores or cells dry, and this willfacilitate the more ready flow of the creosote oil along the walls ofthe pores or cells of the wood, thus facilitating and expediting thecoating. of said walls with creosote oil.

Furthermore, the heating of the air in jected into the wood will serveto melt most of the gums or resins remainingin the wood and prevent thesame from clogging up the cells or pores against the entrance 0 theheated air.

The time durin which the wood should be subjected to t e action of theheated creosote oil would depend in a large meassure upon the nature ofthe wood being treated, being, of course, greater with dense woods thanwith porous woods, and the time required would also be greater when thewood had not been thorou hly seasoned than where it had been wellseasoned or dried.

After this treatment with the heated creosote oil has been continued fora suitable length of time, the creosote oil is drawn off from theretort, and the pressure is suddenly relieved. This will cause theimprisoned air to blow the free creosote oil out of the cells or poresof the wood, and it will settle in the bottom of the retort and ma bedrawn oil for use over again.

11 this final step of relieving the pressure, the pressure may be simplylowered to normal atmos heric pressure; or, if preferred, a artia vacuummay be created, which wil ex edite the escape of the imprisoned air romthe cells and the conse uent blowing out of the free creosote oil. 1 heprocess maybe stated briefly as folows:

The wood, preferably in the form of timber of the dimensions reguiredfor use, is subjected to the usual rying process either by air seasoningor by kiln drying, and is then placed in the retort, which is closed andcontains more or less air, also the air imprisoned in the pores or cellsof the wood, under atmospheric pressure.

1 preferably increase the density of the air by forcing in additionalair'under presi sure.

This air is heated and maintained in the heated condition until it warmsup the wood and penetrates the pores and cells thereof. Now the heatedcreosote oil is forced in under a still higher pressure, compressing theair in the pores, cells and cavities of the wood and coating the sidewalls of these pores, cells and cavities, as hereinbefore described; andfinally the pres sure is removed and the excess of creosote vacuum inthe retort, which may be done by means of an air ump.

The air imprisone in the cells, pores and cavities of the wood will blowout the free oil,'and the de ree of permanent saturation of the woodspective pressures of the heated air before the creosote oil isadmitted, and of the pressure to which the heated creosote oil issubjected in carrying out that step of the process.

, After the operation has been completed, the walls of the cells orpores of the wood will be coated or painted with a more or less thinfilm or layer of creosote oil, and these walls havin been previouslydried, this film or layer oi creosote oil will oxidize and harden, andwill form a thin solid shell or paint on the inner walls of the pores ofthe wood, which will effectually protect the same from the incursions ofdestructive insects, or living germs.

The oxidizing and hardening of the film or layer of creosote oil will beexpedited by the use of heated air under pressure in the manner stated.

This hardening of the creosote oil on the walls of the cells or poreswill also do away with any dripping or exuding of the creosote oil fromthe wood. By preventing the exudation of the oil from the wood sotreated, not only is much serious inconvenience in the handling of suchmaterial avoided; but one great objection to they use of such treatedtimber for telegra h oles, fence posts, or the like is avoide w erethese are used near wells, or springs, or other reservoirs containingdrinking water, which is likely to be contaminated by the exuding of theoil from the timber. It has been found in practice that a very smallamount of creosote oil exuding from a telegraph or fence post will oftencontaminate a neighboring well or pond and render it unfit for drinkingpurposes for either man or beast.

Again, the wood so treated will have its interior pores or cells coatedwith a comparatively hard shell or paint adapted to hold spikesor'nail's driven therein; whereas creosote oil when used to saturaterailroad ties or the like forms with the wood a greasy mass in whichspikes or nails will not firmly adhere. This is especially noticeablewith railway ties, treated by the old method. of thoroughly saturatingthe tie with creosote oil, in which cases the spikes often became loose,due to the vibrations to which the rails were subjected.

While the hereinbefore described process is specially applicable to theuse of creosote oil, as a preservative; it is also specially applicableto the use of asphaltic oils, crude oils of asphaltic basis tar oilmixtures, crude oil mixtures, and the like, with or will depend upon there''- without the addition of chemical constituents ot' aseptic orantiseptic qualities.

l'nder certain conditions the process may also be satisfactorily usedwith other preservative aqueous solutions such as zinc chlorid, or otherwell known liquid preservatives.

By having the heated air supplied to the retort at a considerably higherpressure than the atmosphere, and permitting this heated air underpressure to completely till of the liquid, so that where the pressure ofthe air is substantially the same as the pressure of the liquid. thetendency of the liquid to enter the pores will be due entirely tocapillary attraction; whereas, as the pressure of the liquid becomesgreater than that of the imprisoned air, the air will occupy a less andless space in the pores or cells of the wood, so that by regulating theinitial pressure of the heated air and the subsequent pressure of theliquid supplied, .the proportion of the liquid injected in the wood maybe predetermined; and, if desired, only a small quantity of the liquidmay be forced into the pores or cells of the wood, capillary attractioncausing this liquid to follow the walls of these pores or cells.

Thus it will be seen that where the initial pressure of the heated airis comparatively high, relative to that. of the liquid, a far smallerquantity of liquid will be sufficient to paint the walls of the cells orpores than where the pressure of the heated air was lower compared tothe pressure of the heated preservative liquid applied in the secondstep of the process. 1$ oreover, the larger the proportion of spaceoccupied by the 1m prisoned air, the greater will be the effect of thatair in blowing the free liquid out of the pores or cells of the wood.

This feature of decreasing the amount of preservative fluid left in thetimber is especially important where extremely porous woods are used,such as young pine trees, or other woods of like nature.

Thus it will be practicable to thoroughly coat the Halls of the pores orcells of any porous wood with a thin layer of protective material whichwill thoroughly preserve this wood without any waste of preservative andalso to obviate the disadvantage as to exuding of the preservative, aspreviously referred to.

It will thus be possible to vary the amount of preservativeleft in thetimber by varying the relative pressures of the preliminary treatmentwith heated air, and the following treatment with heated preservativeliquid, so that within limits the desired amount of liquid may be leftin the timber, and at'the same time the walls of the pores, cells orcavities of the wood would be thoroughly protected against theincursions of those insects or living germs which tend to destroy thewood.

Having thus described my invention what I claim and desire to secure byLetters Patent of the'l nited States is:-

1. A method of preserving wood which consists in placing the wood in aclosed retort, subjecting the same to the action of heated air underpressure, then injecting heated creosote oil into said retort at ahigher pressure until the wood is submerged therein, maintaining thewood in said heated oil bath under high pressure until the walls of thepores and cells of the wood are coated with creosote oil. then drawingoff the excess oil, and finally relieving the pressure, thus allowingthe air -imprisoned in the wood to escape.

2. A method of preserving wood, which consists in placing the wood in aclosed retort, subjecting the same to the action of heated air underpressure, then injecting heated creosote' oil into" said retort at ahigher pressure until the wood is submerged therein. maintaining thewood in said heated oil bath under high pressure until the walls of thepores and cells of the wood are coated with the creosote oil, thendrawing off the excess of oil, and finally relieving the pressure andcreating a partial vacuum in the retort, thus allowing the airimprisoned in the wood to escape.

In testimony whereof, I afiix my signature.

MAX RUPING.

\Vitnesses:

HENRY HASPER, ALLEN J. JENNINGS.

